Starting and operating circuits for electric discharge devices



Feb. 22, 1949. I R. v. MILLS ETAL 2 5 STARTING AND OPERATING CIRCUITS FOR ELECTRIC DISCHARGE DEVICES Filed June 9, 1947 I lnven bor s:

Eober' tr V. MiLLs Maurice GcLar'k e,

HavoLd E.PL1++,

Their A cborneg.

Patented Feb. 22, 1949 STARTING AND OPERATING CIRCUITS FOR ELECTRIC DISCHARGE DEVICES Robert Victor Mills, Maurice George Clarke, and Harold Robert Ruff, Rugby, England, assignors to General Electric Company, a corporation of New York Application June 9, 1947, Serial No. 753,462

In Great Britain October 31, 1946 7 Claims. (01. 315- 96) This invention relates generally to electric discharge devices of the type employing ionizable mediums such as gases or vapors, and more particularly to improvements in starting and operating circuits therefor.

Circuits now in wide use with electric discharge devices such as fluorescent lamps are provided with means for heating filamentary electrodes and for impressing a high voltage for short duration upon the electrodes for starting an are discharge therebetween. Some of these arrangements are provided to delay application of a high voltage until the electrodes have reached electron-emitting temperatures.

Use has generally been made of thermal starting switch the contacts of which are arranged, when the supply circuit is connected to the lamp, to connect the electrodes of the lamp in a series circuit to the supply circuit, thereby supplying preheating current to the electrodes. The thermal switch is so constructed that after a predetermined time period its contacts are open thereby interrupting the series circuit through the lamp electrodes. As a result of the inductance in series with the lamp and which is usually necessary for stabilizing the arc discharge, a voltage impulse is impressed between electrodes when the contacts of the thermal switch open, thus the discharge is started between the preheated electrodes.

If the thermal switch is of the kind having a heating element for actuating a bi-metal element, the circuit is so arranged that during operation sufiicient current flows through the heating element to maintain the switch contacts open so long as the discharge passes between the electrodes.

If the thermal switch is of the glow discharge type, the contacts are normally open and only close for the short period necessary to preheat the lamp electrodes after a glow discharge has persisted for an appreciable period.

In the event that the discharge fails by reason of an interruption in the supply, the thermal switch ultimately closes its contacts in commencement for, or as a part of, the cycle of operations above described. If the interruption in the supply is only momentary, i. e., less than onefifth second, the discharge through the lamp is maintained and no alteration in the elements of the operating circuit takes place. If, however, the supply voltage fails for a longer period, i. e., of the order of one-half second or longer, the discharge through the lamp ceases and the lamp ees out fo a period of. the order of twenty seconds necessary for the contacts of the thermal switch to close and recommence the starting operation.

In the case of lamps operating from a source of current subject to frequent interruptions, which conditions apply to vehicles used in connection with electric traction systems, this delay is ob.- viously disadvantageous where it is desiged to restart the lamps promptly. Furthermoge, on such systems the supply voltage, while not necessarily failing, may be reduced to a value such that the discharge through the lamps cannot be main.- tained. The lamps then go out and are re-started only after the time delay above referred to.

The object of our invention is to provide a new and improved starting and operating circuit for electric discharge devices.

Another object of our invention is to provide an operating circuit for an electric discharge lamp in which the time delay element is removed.

A further object of our invention is to provide a new and improved circuit which will not be in-, fluenced by the frequent interruption or voltage variations in the supply circuit.

In-accordance with the present invention relay means having its contacts connected in the series circuit inter-connectin the lamp electrodes for the purpose of supplying preheating current thereto from thesource, is arranged to be responsive either to the supply voltage or to. the voltage across the lamp (or lamps when two or more are supplied in series or parallel) when the discharge therethroughceases, thereby restoring continuity in the electrode heating circuit when the supply voltage fails or diminishes to a predetermined extent below the normal value, the relay -means having imparted to it such a time delay as to prevent operation'for momentary interruptions or diminutions in the supply voltage.

In carrying out the invention in one embodiment, the contacts of the relay means, such as a magnetic relay are so included in the series circuit through the lamp electrodes that as soon as a starting means operates the relay opens its contacts thereby producing in conjunction with a serially connected ballast a starting impulse voltage and maintains open the series preheating circuit so lon as the lamps remain in the cons ducting or operating condition. Thus, when the lamp is extinguished, that is to say as result of interruptions in the supply voltage lasting for more than one-fifth second, the relay closes and immediately completes the preheating circuit through the lamp electrodes thereby re-initiating the above described cycle of operation.

When a starting means such as a thermal starting switch employing a separate heating element is used this starting switch is included in the series circuit between the lamp electrodes. The heating element and the starting switch are also in the series circuit. Thus, when the supply circuit is first connected to the lamp the relay is deenergized and the starting switch contacts are closed and preheating current fiows through the lamp electrodes. The electrodes are thereby heated to operating temperature. The relay then picks up, opens its contacts after the contacts of the starting switch have opened, and maintains the preheating circuit open, thus allowing the element of the starting switch to cool and its contacts to close, thereby pre-set for an immediate further start should the supply voltage fail and the relay contacts close.

When, however, the thermal switch is dispensed with, the contacts of the relay directly complete the series circuit through the lamp electrodes, and the time delay imparted to the relay is sufficient for its contacts to open only after the lamp electrodes have been preheated to an operating temperature. Such an arrangement, however, may involve undue arcing of the contacts of the relay and this may be avoided by the use of a second relay controlled by the first relay and connected across the supply circuit and arranged to be energized only when the first relay is actuated, the normally open contacts of the second relay being arranged in the series preheating circuit so as to be closed when the second relay is energized by the closure of contacts in series with its actuating winding and controlled by the first relay.

The arrangement is suitable for application to the energization of two or more lamps connected in series, in which case the magnetic relay will be provided with two independent sets of c tacts each arranged in shunt with the discharge space of a difierent one of the lamps, and when closed complete the series preheating circuit for all the lamps. Only one thermal switch (if used) is then required in conjunction with one of the lamps.

In order that the nature of our invention may be more clear, we now describe, with reference to the accompanying drawing two circuit arrangements embodying our invention. Fig. 1 is a diagrammatic view of electric discharge devices and a starting and operating circuit therefor suitable for use with alternating or direct current systems incorporating our invention. Fig. 2 illustrates a modification of the circuit arrangement of Fig. 1.

Referring to Fig. 1, discharge devices I, I therein comprise elongated tubular or cylindrical envelopes 2, 2 having sealed into the ends thereof thermionic electrodes 3, 4 and 5, 6, respectively, which may be of the filamentary type each herein illustrated as comprising a coil, preferably of a coiled coil of tungsten wire activated with usual mixtures of alkaline earth metals such as barium or strontium oxides. .The envelopes 2, 2 contain ionizable mediums. These ionizable mediums may comprise a rare gas like krypton, neon, argon, or mixtures thereof at a pressure of a few millimeters and a small quantity of mercury, which during operation of the lamp has a low pressure of the order of ten microns. The devices I, I may be low pressure positive column lamps of the fluorescent type with a suit-' able phosphor or fluorescent coating. This fluorescent coating upon excitation by the radiation produced by an electric discharge between the electrodes, transforms the shorter-wave radiation due to the discharge into longer-wave radiation such as radiation within the visible range.

The electric discharge devices I, I are connected in series with a ballast impedance or reactance I, and, if necessary, an inductance 8 across a power supply 9. ,One end of electrodes 3 and 4 of device I are connected in series with a thermal starter switch ID having its heater coil I I and switch contacts I2 and I3 connected in series, and a pair of normally closed contacts I4 of a magnetically operated relay I5. One terminal of both electrodes of the electric discharge device I are connected across another pair of normally closed contacts I6 of the magnetically operated relay I5. An actuating coll ll of the relay i5 is connected across both electric discharge devices I, I.

When a potential is applied to the cricuit, current flows through the filamentary electrodes of the lamps and the heater coil of the thermal switch I0. After a predetermined heating period contacts I2 and I3 of the thermal starting switch I0 open, thus applying the supply voltage across coil I! of the magnetically operated relay I5. The relay I5 will then open its contacts I4 and I 6 and an arc discharge will occur within the electric discharge devices I, I due to production of an impulse of voltage by the rate of change of current through impedance 1 and inductance B or both. The change of the current through the inductance 8 produces a surge across the electric devices which assist in striking the arc discharges therein. As the current through the heater. I I of the thermal starting switch ID has been interrupted, its contacts I2 and I3 will re-close. The magnetically operated relay I5 is constructed to provide such an opening time delay that with short interruptions in the supply voltage the relay contacts I4 and I6 will remain open but with longer interruptions the magnetically operated relay I5 will be deenergized thereby closing contacts I4 and I6. When the power supply is removed the normal starting operation will be repeated giving adequate electrode heating. Thus, the normally closed contacts I4 and I6 undergo a closed-open cycle of operation to. initiate conduction by discharge devices I, I.

On certain traction lighting circuits it has been found that the voltage does not fall to zero during power supply disturbances. Under such conditions the reduced voltage may not be sufllcient to maintain an arc discharge within the lamps, but may be suflicient to maintain actuating the associated relay. Thus if the lamps extinguish they will not re-strike when the normal supply voltage is resumed. Fig. 2 shows a further arrangement by which satisfactory operation may be obtained under these conditions. As in the previous arrangement the lamps are connected in series with a stabilizing impedance or reactance I across the supply circuit 9.

In this embodiment of our invention we provide a relay means selectively responsive to prede-,

termined range of voltages and which may comprise a plurality of interconnected magnetically operated relays to control the starting and operation of the electric discharge lampsfI and I. For example, we provide a magnetic relay I8 having an actuating coil I9 and contacts 2 This relay is selectively responsive to the voltage appearing across the serially connected lamps! ,and I, and its actuating coil I9 is connected across the tar amazes or outside terminals of the serially connected lamps. In order to provid the relay l8 with a predetermined'time delay; weconnect across the terminals of the actuating coil ill a cond'enser2i'.

A second magnetically operated, relay 22, controlled by relay l8, comprises an actuating coil 23 and'two sets of contacts 24- and 25, respectively, connected across electrodes of-lamps l and I". Actuating coil 23 is connectedin series-relation with contacts 20 of relay l8 across the supply circuit 9.

The purpose of the capacitor 2| across relay [8 is to provide a time delay both on opening and closing the relay. Relay I8 is set so that it will operate in response to a predetermined voltage, such as a voltage greater than the total normal operating voltages of lamps I and I. This condition prevails when no arc current is flowing through the lamps or under abnormal operation of the lamps. It is not operated by the total voltage drop of the lamps during normal operation or conduction.

The operation of the circuit is as follows: When the supply voltage is applied to the terminals of the system, coil I9 is energized closing the contacts 20 and energizing the coil 23, thus closing contacts 24 and 25. Current then flows through the lamp electrodes and th voltage across coil ill will be reduced to the voltage drop of these lamp electrodes. After a time delay, adjustable by the value of the shunt capacitor 2|, the energization of the relay I 8 will be decreased thereby opening contacts 20 and de-energizing coil 23. Contacts 24 and 25 will open causing the lamps to conduct. Thus the contacts 24 and 25 of relay 22 controlled by relay [8 undergo an open-closed-open cycle of operation to initiate conduction of the lamps. As in the previous arrangement for short breaksin the supply voltage the relays will not operate, but for longer interruption both relays will remain open and when the supply voltage is resumed the starting operation will be repeated. The purpose of utilizing two relays is to insure that contacts 24 and 25 move quickly, thus minimizing arcing at these contacts. Due to the retarding effects of the condenser 2| the contacts 20 associated with coil l9 tend to move slowly.

It will be appreciated that the above arrangement may be effected with one relay having a suitable time delay and movement designed to eliminate undue arcing at the contacts.

If it is desired to prevent repeated operation of the starting relays should a lamp fail to strike, a thermal device may be connected with its heater in series with contacts 25 and its contacts arranged to short contacts 20 after a predetermined number of starting operations.

6 'ealclnofi the type employing amionizablemedium andvcomprisinguat least one electrode ofithe; filamentary type and a cooperating; electrode; a ballast reactance connected? in series relation with said devices across said: supply. circuit, and magnetic relaymeans responsive to the voltage of said supply circuit andivoltagebelow a predetermined valueofsaidsupply circuit voltageifor. controlling .the starting and operation of saidv discharge devices,: said. relay nieans comprising am actuatin coil connected across the/plurality of discharge devicesr-and having'sets of contacts. respectively connectedacross the: various. discharge device's;v

3, In combination, a supply circuit, 'a; plurality of serially: con-nected .el'ectric' discharge devices each having an electrode of thefilamentary type and a cooperatingi electrode, a ballast reactance connected in series relationwith said devices across said circuit, and magnetic relay means responsive to the voltage across said discharge devices and having sets of normally closed contacts each connected across a .difierent one of said discharge devices, said magnetic relay means being selectively responsive to the voltage across said serially connected devices to maintain said contacts open after initiation of arc discharges within said devices.

4. In combination, a supply circuit, a plurality of serially connected electric discharge devices each including a filamentary electrode, a ballast reactance connected in series relation with said devices across said supply circuit, a time delay magnetic relay means connected across said devices and responsive to the voltage of said supply circuit, and a second magnetic relay means controlled by the first mentioned relay means and having an actuating coil connected to be energized from said supply circuit and having sets of normally open contacts respectively connected across electrodes of different discharge devices.

5. In combination, a supply circuit, a plurality of serially connected electric discharge devices each comprising at least one filamentary electrode, a reactance connected in series relation with said discharge devices across said circuits, and a magnetic relay means and a thermal means for starting and controlling the operation of said discharge devices, said magnetic relay means comprising an actuating coil responsive to the voltage across the serially connected discharge devices and having normally closed contacts connected across electrodes of each of said de- The above arrangements may be used to operate nected discharge devices and having contacts connected across electrodes of each of said devices.

2. In combination, a supply circuit, a plurality of serially connected electric discharge devices vices, and said thermal means comprising a heater coil, lei-metallic element and normally closed contacts in series with one pair of said relay contacts connected across the electrodes of at least one of said devices.

6. In combination, a supply circuit, a plurality of serially connected electric discharge devices each including a filamentary electrode, a ballast reactance connected in series relation with said devices across said supply circuit, a time delay magnetic relay means comprising an actuating coil and normally open contacts, said actuating coil being connected across said devices and responsive to the voltage of said supply circuit, and a second magnetic relay means controlled by the first mentioned relay means and having an actuating coil connected to be energized from said supply circuit and having sets of normally open contacts respectively connected across electrodes of different discharge devices, said'normally open contacts undergoing an open-closed-open cycle of operation to initiate conduction of said devices,

7. Ira-combination, a supply circuit, a plurality of serially connected electric discharge devices REFERENCES CITED each comprisingat least one filamentary elec- The following references are of record in the trode and a cooperating electrode, a reactance fil Of h P n connected in series relation with said discharge UNITED STATES PATENTS devices across said circuit, and magneticv relay means for starting and controlling the operation Number Name Date of said discharge devices and comprising an. ac. 2,112,718 Somers Mar. 29, 1938 tuating coil responsive to the voltage across the 3 1 Frech July 1944 .m rially connected discharge devices and having 10 no -'i= J" ,otacts connected across the electrodes of each ofs'ai'd devices, said contacts undergoing a closed-open cycle of operationto initiate discharges within said lamps.

v I ROBERT VICTOR ms. 15

MAURICE GEORGE CLARKE. HAROLD ROBERT RUFF.

Certificate of Correction Patent No. 2,462,328. February 22, 1949.

ROBERT VICTOR MILLS ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 17, claim 3, strike out the words and a cooperating electrode and insert the same in line 45, claim 5, after the syllable trode and before the comma;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11th day of October, A. D. 1949.

THOMAS F. MURPHY,

Assistant Uommz'ssioner of Patents. 

